Electrically conductive polypyrrole (PPy) was functionalized with heparin (Hep) to improve its surface biocompatibility. Heparin, which is a bioactive polyelectrolyte. was used as the doping anion. The immobilization of Hep in PPy was facilitated by the use of a nanoporous membrane which acts as templating substrate. In this way we have synthesized nanostructured electrodes based on polypyrrole and heparin as hollow tubules. The aim of this study was to determine the influence of the electrosynthesis parameters (monomer concentration and electrolyte nature) on the morphology and kinetics of the PPy nanomaterials in view of their possible, long-term biomedical applications. (C) 2007 Elsevier Ltd. All rights reserved.